I still felt like a bit of a fraud afterwards (INFJ high standards can be a real pain in the proverbial at times!). I used to possess a near photographic memory - for example, I could memorise a complicated diagram or formula and reproduce it exactly on an assignment or exam paper, without ever really knowing what it meant. After a few days, the memory faded away completely, so I had to memorise it a day or two before the due date.
At the end of the day does it really matter to anyone but us? Most people would say that if we obtained a good grade in a subject than we have succeeded, regardless of our personal feelings of inadequacy. Many of the subjects I studied have never cropped up in my life again, and even if they do, I can simply refer back to a textbook (or, these days, the internet).